Wall Insulation in Duluth, MN

Wall insulation is the fix for rooms that stay cold no matter how high the thermostat goes. A large share of Duluth's houses were built before insulation went into walls as a matter of course; the city's housing market analysis puts the share built before 1940 at about 44 percent. In many of those homes the exterior walls are hollow, or hold old material that has settled to the bottom of the cavity.

Closed walls: dense-pack

If the walls are finished and you do not want to open them, we can drill small holes, from outside under the siding or from inside, and blow cellulose into each cavity at high density. Dense-packed cellulose fills around wiring and blocking and slows air movement through the wall. HomeGuide lists dense-pack at $1.60 to $4.20 per square foot. We check each cavity for fill and plug and patch the holes.

Open walls: spray foam

When walls are open for a kitchen, bath, addition or gut remodel, spray foam goes directly into the stud bays. Closed-cell packs the most R-value into a thin 2x4 wall and adds air sealing. Open-cell costs less and seals air but has lower R-value per inch. Fixr lists foam in existing walls at $3.15 to $7.50 per square foot and in new construction at $2.75 to $6.50.

Before we fill a wall

We look for knob-and-tube wiring, which should be checked by an electrician before it is buried in insulation, and for signs of water getting into the wall from outside. A leaking window or failed siding needs to be fixed first.

What changes after

Filled walls cut drafts at outlets and baseboards and even out the temperature from room to room. In a hillside house that takes wind off the lake, the difference is noticeable.